Method of and means for forming coils



Aug. 5, 1947. G. H. ERB 2,424,974

METHOD OF AND MEANS FOR FORMING COILS Filed April 24, 1943 gfli r:

I I l 1 l6 4 Q 50 a 53 2,2 24 GEO/176E 1 EAB INVEN TOR.

ATTORNEY Patented Aug. 1947 METHOD OF AND MEANS FOR, FORMING COILS George H. Erb, South Orange, N. L, assignor to Federal Telephone. and Radio Gorporation, Newark, N. JA, a. corporation of Delaware Application April 24, 1943; Serial No. 4843356 5'- Claims.

This invention relates tomethods of and means for forming coils; and more particularly to an arrangement for forming internally wound coils.

An object of this invention is to provide novei methods of and means for forming internallywound coils.

Another object of this invention is directed to the provision of a novel collapsible; coil-forming; mandrel.

A specific feature of the present invention is' the windingoi a coil onthe threads of a colla-psible threaded mandrel, screwing this mandrel into an internally threaded coil form and depositing the coil on the mandrelinto the threads of the coil form by collapsing and withdrawing themandrel.

These and other features; capabilities and ad'- vantages of the invention will appear from sub-'- joiningdetailed description of one embodiment and a modification thereof, illustrated in theac companying drawings; inwhich:

Fig; 1 isa longitudinal cross-sectional View of a coil form showing the coil-romping mandrel of the present inventionpartia-l-ly inserted;

Fig. 2 is an end view of the exposed end of the coil-forming mandrel of Fig. 1;

Fig. 3 is an end View of the other end of the coil-forming mandrel.

Fig. Lisa: partial enlarged view of: the threaded portion of the coil-forming mandrel;-

Fig. 5 is 5. partial threaded portion of a modifled form of coil-forming mandrel.

In the. making of internally wound coils: such, for example, as. an internally wound potentiometer or rheostat, in accordancev with thepresent invention and as seen in Fig. I, 1' start with an internally threaded insulated coil form tit into which is screwed a. coil-carrying, collapsiblemandrel generally indicated at it. This mandrel L2 is formed as. a. built-up structure comprising a central core: L4 surrounded-by attached segments ES and I8, threadediorthe greater part oi their length and so shaped as to form about the core [4 a threaded cylindrical structure. If the segments I6 and I8 are formed of relatively rigid material for example, brass, they need be connected to the core M at one end only as by pairs of screws 20.

The threaded portions of the segments 16 and 18 are so designed thatwhen these segments are properly assembled on the core I4 the threads on any one segment are aligned with the threads on adjacent segments to form a continuously threaded structure whose threads are of the same pitch. as the internal threads in the coil sum 2 Iii. According to one proposal, for example, inthe potentiometer disclosed my copending applicatibn, N. 484,355; filed April 24, 1943, it may be advantageous to form a double wound coil,

in which case the threads: on the mandrel l2 and the coil support I l! will be double threads. Coils 2 2' and 24 are: wound on the apices of the double threads and the ends of the coils may be held place at one end by means of the assem- Idling screws 20, on the other end by means of a-remova-b-le plug 28, as is more clearly shown in Fig; 3a In order that the coil wires be fitted on the apices of the threads of the mandrel, as seenin Fig. 4. each thread til and 3 2 may be fo-rmedwith: grooves $4- and 3E respectively,

' thethreads 3d and 325 formed about. the mandrel t2, the ends being tieddown to the mandrel. in any suitable manner by utilizing the holding screws 20 at one end and inserting. the removable plug 26 at the other end. The mandrel l2 with the coils wound on it then screwed into the coil term: I 0. When the: mandrel I 2 is screwed. into its. final! position the: screws 21!: are removed, releasing: thesegments It? and? I 8 from the coreit. The plug w is: also withdrawna and the core I15 is: pulled out. from. among: the assembled: segments'. F'orithis purposecore 141 may be made slightly longer than the segments IE 1-3,. as indicated in 1,. and: may be provided with. a bore. 3 l or any suitable: means: with which a tool: ilor nailing: out the: core may be used.

the core 14. is withrlrawn the segments id and It are c'olllapsedinwardlyand carefully removed, the coils 22 and 24 on their apices automatically springing out under their own resiliency into the bottom of the internal threads formed with the coil form [0. These coils 22 and 24 will stay in the bottom of these internal threads under their own spring action and the ends of the coils can be held in place in any suitable manner. On the inner end of the coil form In a passage or passages 28 may be provided for withdrawing the inner leads of the coils if contact thereto is desired.

It is to be pointed out that while for the purposes oi illustration I have described 59y inva tion in connection with a double coil utilizing a double-threaded mandrel, it will be obvious to those skilled in this art that the invention is equally applicable to a single coil utilizing a single threaded mandrel. It will also be noted that in the form of invention illustrated I have formed the outer surface of the cor 14 as a, hexagon surrounded by six segments, three small segments (6 and three larger segments I8. The number of segments, however, will depend upon the size of the coil to be formed and the size of the mandrel necessary, the criterion to be kept in mind being the number of segments required to permit collapse and withdrawal of the individual segments after the core 14 has been removed. Generally speaking, the greater the diameter of the mandrel and the coil to be formed, the greater the number of segments required. Likewise, the greater number of segments necessary results in a greater number of sides or bases formed on the core l4, but these need not necessarily be made plane as in the example given.

It is also possible to wind a double coil in accordance with the present invention by winding the two coils both on the apices and between the threads of a single threaded mandrel as illustrated in Fig. 5. As there illustrated, the collapsible mandrel I2 is formed of segments [6 and I8 which may be identical with the corresponding segments shown in Fig. 1 except that they are single threaded instead of double threaded. The coils 22' and 24 are wound upon both the apices and the bottoms of the single threads and, upon collapse of the mandrel within the coil form, the wires will be respectively deposited in the bottoms and on the apices of the threads of the internally threaded form, In all other respects the method and means will be the same as previously described, except that slightly greater care may be required in removing the threaded segments after withdrawal of the core.

While I have described above the principles of my invention in connection with certain particular coils, coil forms and mandrels, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of my invention as set forth in the objects and the accompanying claims.

I claim:

1. The method of forming an internally wound coil, which includes the steps of winding the coil on the apices of the threads of a threaded collapsible mandrel, screwing the mandrel with the coil thereon into an internally threaded coil sup- .port, and then collapsing and withdrawing the mandrel, leaving the coil in theinternally formed threads of the coil support.

2. The method according to claim 1, in which said threaded nandrel is formed by a central core surrounded by a plurality of aligned, threaded removably attached arcuate segments, and in which said mandrel is collapsed and withdrawn 4 by disengaging said segments from the central core, withdrawing the central core and then inwardly collapsing and withdrawing the individual arcuate segments,

3. The method according to claim 1, which includes the step of winding a second coil portion in the bottom of the threads on the collapsible mandrel and depositing this second coil portion on the apices of the internal threads of the coil support upon the collapse and withdrawal of the mandrel.

4. Coil-forming apparatus including, in combination, a collapsible mandrel comprising a longitudinal central support, a plurality of arcuate segments removably fastened to said support, said segments being so correlated as to form together an outer cylindrical surface and being threaded for the greater part of their length, the threads on one segment meeting the threads on the adjacent segments so as to form a complete thread over the greater part of the mandrel, the apices of the threads being formed with a wire-receiving depression, whereby a wire coil may be wound in said depression to complete the threads on the threaded mandrel, and an internally threaded coil support adapted to receive the threaded mandrel, whereby, when the mandrel carrying the coil is wound into the threaded support and the mandrel is collapsed by removing the central support and the attached threaded segments, the coil seats in the bottoms of the threads in the coil support.

5. A collapsible coil-winding mandrel including, in combination, a longitudinally extending central support, a lurality of longitudinally extending arcuate segments removably fastened about said central support, said segments being so correlated as to form together an outer cylindrical surface, and being externally threaded for the greater part of their length, the threads on one segment meeting the threads on the adjacent segments so as to form a continuous thread over the greater part of the mandrel, the apices of the threads being formed with a wire-receiving groove in which :the wire of the coil to be formed is wound.

GEORGE H. ERB.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Haas et a1 July 27, 1943 

